Ib Chorkendorff - the catalyst for tomorrow’s energy

Climate-neutral challenges

If Denmark, the EU and, hopefully, the rest of the world are to be climate-neutral by 2050, it will require a massive effort. Much of the need for energy can be met through renewable energy sources such as solar and wind power. However, some of the major challenges involve storing energy over long periods of time, manufacturing chemicals and developing fuels for, for example, aircraft.

Ib Chorkendorff says he regularly flies to San Francisco to meet with his partners at Stanford University. “The plane weighs 300 tonnes at take-off, of which 100 tonnes is fossil fuel. If the plane were to be powered by batteries instead, it would weigh 14 times as much. We need a synthetic fuel which is produced using renewable resources.” The development of electrofuel (or synthetic fuel) is one of the focus areas at Ib Chorkendorff’s research centre.

One of the other activities is developing chemicals for manufacturing paint and plastics, for example, which are currently based on fossil fuels. Solutions must be found.

However, one of the really big challenges that is central to food supplies is being able to produce nitrogen fertilisers. Nitrogen has always been a limiting factor in agriculture. Some of the nitrogen fertiliser comes from the livestock’s urine, which is part of the slurry. The rest is produced artificially by producing ammonia (NH3). This requires a lot of energy, and takes place at large industrial plants. Ib Chorkendorff says that “today, producing ammonia accounts for approx. 1% of the world’s energy consumption.” This is something which can be done in a much more energy-efficient and also more eco-friendly way.

The solution to some of the challenges posed by moving to a climate-neutral society are catalysts. A catalyst is a substance that promotes a chemical process without being consumed itself. Moreover, the amount of energy needed to initiate the process is less when using catalysts, while the reaction rate is higher.

Catalysts are, as we know, found in our cars. Cars need a catalytic converter so that harmful exhaust gases are converted into harmless compounds. Catalytic converters like those in cars are heterogeneous catalysts, in other words they are in a different phase from the reactors in the process. As a rule, it is metals that help transform gases. Ib Chorkendorff knows all about heterogeneous catalysts – he’s been working with them for decades.

Hooked on catalysts

“When I started university, I had no idea that jobs like this existed,” says Ib Chorkendorff. After upper secondary school, he became a student at the University of Southern Denmark in Odense, studying for a BSc in Natural Science degree, which gives one a broad understanding. In the course of the first couple of years, the subjects medicine, biology, biochemistry and mathematics were peeled away, and he specialised in physics as his main subject and minored in chemistry.

“When I started lab work and meeting the researchers, I realised that I also wanted to become one,” says Ib Chorkendorff. The day after graduating with an MSc in 1985, he received a PhD grant. “That’s what I wanted to do, after all. Discover new knowledge, that’s what I think is interesting.”

During his studies, Ib Chorkendorff was asked to cover for a lab assistant on maternity leave at Haldor Topsøe A/S in Lyngby. The company produces catalysts, and was founded by a civil engineer, Haldor Topsøe. “Haldor was, of course, taught by Niels Bohr. He took a keen interest in science. He also funded a lot of basic research.”

Haldor Topsøe’s company owned a machine that could examine particle surfaces and their ability to catalyse chemical processes. It was one of the first such pieces of equipment for surface analysis in Denmark. Ib Chorkendorff’s task was to maintain the machine. “I was there for six months, after which I was hooked on catalysts.”

After his PhD, in 1986 Ib Chorkendorff was employed as a postdoc in the USA, working with catalysis and surface physics. A research career within catalysts was well underway. Today, his 40-strong research team works with the production and testing of new catalysts.

Making catalysts

A catalyst can be produced on a large scale by chemical synthesis, providing you know what it needs to look like. However, if you are going to develop a brand new catalyst, and find out exactly how it works, more is required.

Ib Chorkendorff’s laboratory has a machine which is today’s equivalent of the one which was at Haldor Topsøe. It is six metres long, made of steel, and is equipped with viewports similar to those on a diver’s helmet. Inside, the pressure is 13 times (one millionth of a billionth) lower than outside. It is an ultra-high vacuum chamber, which makes it possible to work undisturbed by the oxygen in the air.

Inside the machine, one works with a material which might be an alloy of selected metals. The aim is to optimise the surface of the material, because it is on the surface that the reactions take place. This is why it is split into nanoparticles. Afterwards, the nanoparticles can be covered in a layer of atoms from another element. This can both reduce material costs and increase the ability of the nanoparticles to catalyse chemical processes.

“So, by manipulating where the atoms sit on the surface, we have a nanoparticle where the surface becomes many times more active,” says Ib Chorkendorff.

At one of the machine’s viewports sit the most important items of all – a scanning tunnelling microscope (STM) and an electron microscope. Using them, it is possible to study the nanoparticles’ surface. 

“Basically, you can see individual atoms. You know exactly what’s happening at the atomic level. I’ve always found this to be extremely fascinating. We want the atoms to sit in a very specific way, because then we can make comparisons with quantum mechanical calculations.”

During the process, the nanoparticles are tested for their catalytic abilities. “Perhaps it doesn’t work at all. We then go back to the theoreticians and discuss possible explanations. We can try and find out why it’s not working, and whether we can come up with something new. This is how we develop catalysts. It’s certainly not a linear process.”

When they know exactly what the nanoparticle should consist of, and what it should look like to function optimally as a catalyst, it has to be possible to manufacture it by means of chemical synthesis, otherwise it won’t be possible to upscale it industrially.

It must be usable

Cooperating with industry is important for Ib Chorkendorff. When he returned from the USA, he wanted to leave academia, and applied for a post at DTU. “The reason I applied for a job in Denmark is that I wanted to work with practical solutions. There is a technical aspect.”

Haldor Topsøe had asked DTU to start conducting research into catalysts. Ib Chorkendorff was employed in 1987 to work with experimental physics in the field. “Jens Nørskov, a theoretician, and I were employed at the same time to start this up. He was in charge of the theory, while I looked after the experiments.”

Now, more than 30 years later, Jens Nørskov and Ib Chorkendorff still have a very constructive working relationship. The two men are two of Denmark’s top researchers. Since 2018, Jens Nørskov has been a Villum Kann Rasmussen professor at DTU after eight years as a professor at Stanford University in California.

Over the years, both Ib Chorkendorff and Jens Nørskov have headed several research centres. They have each run a 10-year basic research centre, funded by the Danish National Research Foundation. Now they are both professors at the VILLUM Center for the Science of Sustainable Fuels and Chemicals (V-SUSTAIN). Most of the research centre is located at DTU, while they cooperate with Stanford University, the University of Southern Denmark and the University of Copenhagen. The centre was established with a one-off award from VILLUM FONDEN in connection with the 75th anniversary of the VKR Group in 2016. The award totalled DKK 150 million over eight years.

“Funding of this kind is very special. It’s a long-term investment. It allows you to pursue an interest over a much longer period. If you have a five or 10-year perspective, it means you can take a few chances. It takes between 18 months and to years to make the big machines I have down here work properly. It’s not like designing a car, where you know exactly what everything needs to be like. These are once-in-a-lifetime machines. They often break, and they always need to be adjusted and optimised to perform their intended function. If you’re going to be out there at the forefront of research, you have to be able to try out new things. This calls for a lot of work, and there is always a risk that it doesn’t succeed. But when it’s a long-term project, then you can afford to take risks.”

If it proves successful, tomorrow’s energy supplies are guaranteed without the use of fossil fuels.

Use of catalysts

As mentioned, catalysts are the solution to many problems. “All our research is about making Power-to-X.” It’s all about using electricity – power – to produce a substance, X. The electricity will come from wind turbines and solar cells. The substance might be ammonia for fertilisers or electrofuel (synthetic fuel) for aircraft.

The synthetic fuel stores the electricity so that the energy can be used when it’s needed. “The most important thing right now is to make hydrogen cheaply, because that is the prerequisite for all the subsequent processes.”

In producing ammonia, the aim is to develop a catalyst that works electrochemically so that it does not have to be under pressure or at high temperature, but can be set up decentrally, directly at the farmer in a barn or out in the field. The apparatus must be able to convert the nitrogen content in the air (N2) into ammonia (NH3). The idea is that you will then be able to fertilise the crops just when they need it. In addition, it will help to reduce agriculture’s emissions of nitrous oxide (N2O), a very potent greenhouse gas.

So, catalysts can play a key role in achieving the goal of carbon neutrality by 2050.

Research centre’s catalyst

Ib Chorkendorff is one of the world’s most cited researchers. He is the author and co-author of 367 peer-reviewed articles, and often stands as the last author, acting as a kind of guarantor for both the content and ethics. At the same time, he heads the research unit SurfCat (Surface Physics and Catalysis) at the Department of Physics at DTU as well as the research centre V-SUSTAIN, so he is no longer able to spend time himself in the lab and engage in experiments.

“My job now is to stay up to date, to develop new ideas, raise funding, and to act as a mentor. I work closely with the PhD students, and I think that’s fun. You could say that I’m conducting research through others. If you’re going to develop new ideas, then I think it’s great to sit and swap ideas with other people. And it’s usually there that the brilliant new ideas emerge.”

Fortunately, there is no shortage of ideas. There are also plenty of challenges in making energy supplies climate-neutral. Will it in fact succeed?

“Yes, I believe we’ll succeed. I’m very optimistic.”